1. Field of the Invention
The invention relates to a brake device for braking a movement of an object by mechanical friction, such as the movement of rails relative to a train, or the rotation of a brake disc or a cycle wheel, which brake device comprises:
a basic part with an engagement point for engagement of a braking force which can be exerted via operating means;
a brake block arranged on the basic part for braking the movement of the object by friction, wherein the basic part is movable such that the brake block is movable with at least a substantial transverse component relative to the movement of the object;
resetting spring means for urging the brake block away from the object to a free rest position such that in the case of a braking force smaller than the spring force a space results between the object and the brake block.
2. Brief Description of the Prior Art
A drawback of the existing brake devices is that due to fouling of the pivot points of the brake device the distance from the brake block to the object for braking is not constant. The braking action is adversely affected hereby. When the distance from the brake block to the object for braking is not constant, the path of the braking force is therefore not constant. This is noticeable in for instance the brake pedal or the brake handle.
When a stop is provided against which the basic part lies in rest position, there is still the drawback that the distance between brake block an d the object for braking is uncertain. This is the result of wear of the brake block. The further problem can arise that although the distance between brake block and object for braking is certain, there is an uncertain play in for instance the brake cable.
The above stated drawbacks are prevented according to the present invention, which is characterized by:
a first and a second stop, which stops are arranged at a fixed mutual distance, which first stop determines the maximum distance between the object and the brake block, and which second stop adjusts itself to the contact position, i.e. the position wherein brake block and object make mutual contact, when a braking force is exerted which exceeds the spring force.
The clearance between the brake block and object for braking is determined by the first and second stop. When now the brake block wears, the clearance would become greater. This is obviated according to the invention in that the second stop adjusts itself to the contact position, i.e. the position wherein brake block and object make mutual contact, when a braking force is exerted which exceeds the spring force. The first stop is herein also adjusted in that the stops have been arranged at a fixed mutual distance. Adjusting means can preferably be provided for adjusting the fixed distance between the stops.
A preferred embodiment of the invention comprises:
a first friction part arranged slidably on the basic part;
a second friction part which is pressed under spring load against the first friction part;
wherein both stops are connected to the second friction part.
The adjustment of the two stops is effected in simple manner by the two friction parts. An efficient adjustment can be obtained by setting the spring load.
The friction parts are preferably disc-shaped.
In yet another embodiment according to the invention both stops are formed as the end surfaces of a slot arranged in the second friction part or the basic part and a pin which extends in the slot, is arranged on the basic part respectively on the second friction part and co-acts with these respective end surfaces.
The advantage hereof is that a compact, simple and effective embodiment is obtained.
The invention further relates to a cycle brake for braking a wheel arranged rotatably in a fork, which cycle brake comprises two brake devices, each arranged on an arm of the fork on either side of the wheel, wherein the first friction parts are arranged fixedly on the fork, wherein the brake locks engage on the cycle wheel and wherein the resetting spring means are arranged between the basic parts.
The advantage of the above stated cycle brake is that the brake blocks are always arranged with a fixed clearance relative to the wheel rim. A reliable and predictable braking action is hereby obtained. Furthermore, the braking force is evenly distributed over both sides of the rim, whereby a uniform wear of the brake block is obtained. This enhances safety, since the braking action is always reliable.
Another advantage of the cycle brake according to the invention is that, particularly in the case of cycle races, a wheel can be replaced quickly without the brake having to be readjusted.
In yet another preferred embodiment of the invention the engagement point for engaging a braking force comprises a device for eliminating play between a bowden cable and the basic part, which device comprises:
a first cylindrical bush,
a second cylindrical bush placed slidably in the first cylindrical bush, to which second bush the outer casing of the bowden cable is coupled so as to be resistant to compression and tensile strain and through which the inner cable runs, wherein the second bush comprises on the outside a recess which together with the outer bush bounds a wedge-shaped space;
at least one ball placed in the groove for blocking by wedging action the sliding movement of the second bush relative to the first bush in an axial direction.
When a brake is sought wherein the clearance between brake block and the object for braking is always constant, it is likewise important to preclude play in other parts of the brake system. Wear does for instance occur in the case of a bowden cable whereby play will occur in the cable. Such a cable will moreover have to be readjusted when the brake block becomes worn. The invention therefore provides the above stated adjusting device.
In yet another embodiment according to the invention the device for eliminating play comprises a third cylindrical bush placed slidably between the first and the second bush for engagement on the at least one ball, in order to discontinue the blocking action as desired.
The inner cable can hereby be displaced in simple manner in both directions relative to the outer cable of the bowden cable, whereby the distance between brake block and the object for braking can be increased, which may be desired when the brake blocks are replaced or when the object for braking is replaced. As soon as the brake device is operated again, the fixed clearance between brake block and object for braking is set once again.